An electric double layer capacitor has started to be used for backing up memory of information a device, and further, for an automobile and the like. With respect to an automobile for which a significantly increasing use is expected, an electric double layer capacitor having a low internal resistance is desired since it is effective to use as large electric current as possible in charging and discharging an electric double layer capacitor. In general, the larger a current density in charging and discharging an electric double layer capacitor is, the smaller a capacitance thereof becomes, and the higher a resistance of an electric double layer capacitor is, the larger a decrease in a capacitance becomes. In this respect, it cannot be said that a conventional electric double layer capacitor has a sufficiently low internal resistance, so that a usage in which a large electric current is used such as an automobile has been limited. In general, since an internal resistance of an electric double layer capacitor is mainly controlled by a resistance of an electrode and electric conductivity of an electrolyte solution, a method for lowering the resistance of the electrode and a method for selecting the electrolyte has been attempted.
However, in many cases, there has been a problem in that if an activated carbon having a large capacitance is used as an electrode material for an electric double layer capacitor, an internal resistance of a resultant electric double layer capacitor becomes high. In response to such problems, for example, Japanese Patent Laid-open Publication No. 2002-222741 proposes a method for obtaining an electrode which is a polarizable electrode having a low resistance and a high capacity by enhancing dispersibility of an activated carbon powder and a conductive agent to improve compression force and shear strength. Further, for providing an electric double layer capacitor with well-balanced properties having a large capacitance and a low internal resistance, Japanese Patent Laid-open Publication No. 2000-353642 proposes a method by blending a multiple kinds of activated carbons having different properties such as an activated carbon having a small capacitance and lowering an internal resistance of a resultant capacitor and an activated carbon having a large capacitance and increasing an internal resistance of a resultant capacitor.
Incidentally, in recent years, new carbon materials such as a soot containing fullerene and a residue obtained by extracting the fullerene therefrom have drawn attention, and have been examined for use as an electrode material for an electric double layer capacitor and a secondary battery (Japanese Patent Laid-open Publication No. 2004-221425, Minato Egashira et al, “Carbon framework structures produced in the Fullerene related materials” “Carbon 38 (2000)615-621”).